This invention relates to an air damper operating system of vehicle air conditioners for automobiles and the like and more particularly to an air damper operating system of vehicle air conditioners whose air damper is operated by a rotary type ultrasonic motor.
An ultrasonic motor is coming into practical use in recent year, as an application of a piezoelectric element (hereinafter referred to as PZT) which becomes an origin of an ultrasonic oscillation. A rotary type ultrasonic motor which is a kind of the above ultrasonic motors is constituted by pushing a moving body serving as a rotor to an elastic body serving as a stator which has PZT plastered on its back side with a predetermined pushing pressure by a spring member, inputs into said PZT an alternating current signal whose phase is 90 degrees different from that of said PZT, generates on said elastic body traveling oscillatory waves under the piezoelectric effect of PZT, and operates to revolve said moving body with said traveling oscillatory waves.
Because the revolving speed of the rotary type ultrasonic motor is slower than that of the motor heretofore in use and, in addition, its torque is large, any speed reduction means is unnecessary. Furthermore, because it has holding power when it stops, to is putting to use for an air damper operating system which operates an air damper of vehicle air conditioners for automobiles and the like, such as that indicated in Japanese Utility Model Koho No. 64-24609.
However, the structure of installing the ultrasonic motor was not indicated concretely in the air damper operating system of vehicle air conditioners indicated in the above Japanese Utility Model Koho No. 64-24609.
An operating circuit is necessary to operate an ultrasonic motor, and so an ultrasonic motor and its operating circuit are constituted as a pair.
On that account, for example, in case of an operating system which uses several ultrasonic motors to switch several air dampers of vehicle air conditioners, several operating circuits have to be used. Then, it leads to such a lot of problems that its cost is high and ultrasonic motors cannot be used in a limited space and ultrasonic motors and their operating circuits have to be installed apart from each other.
Heretofore, Japanese Utility Model Koho No. 63-131596 indicates an operating system with several ultrasonic motors which is provided with a switching means to transmit a cycle signal generated from a signal generation means alternatively either to an elastic body of the first ultrasonic motor or to an elastic body of the second ultrasonic motor. However, because the operating system heretofore in use operates the first or second ultrasonic motor alternatively, one ultrasonic motor rotates to a predetermined position an then, another ultrasonic motor rotates to its predetermined position. In consequence, there was such a problem that their simultaneous working could not be done in the same way as two ultrasonic motors were operated by two operating circuits respectively.